Physics Unit 3

The turning effect of a force, which depends on the distance between the point where the force is being applied and the strength of the force applied

1 of 26

How do you work out a moment?

moment = force x perpendicular distance from pivot

2 of 26

What is another name for the centre of mass?

Centre of gravity

3 of 26

Explain non-equilibrium

When an object is being suspended and is to one side, the centre of mass will not be directly below the point of suspension, so the object is said to be in non-equilibrium

4 of 26

Explain the principle of moments

The sum of all moments clockwise around a point is equal to the sum of all anticlockwise moments around that same point

5 of 26

What makes an object topple?

A tilted object will only topple when released if the “line of action” is outside its base

6 of 26

Explain the difference between circular motion and centripetal force

Circular motion is the act of an object travelling around in a circular direction, whereas centripetal force is the idea of the force of the moment always acting towards the centre of the circle

7 of 26

What is load?

the weight being lifted

8 of 26

What is effort?

The force being applied

9 of 26

What is the pivot?

The point around which the lifter lifts the weight

10 of 26

What is meant by the centre of mass?

If the weight of an object were to act at a single point, this is the centre of mass

11 of 26

When is an object in equilibrium?

A suspended object is in equilibrium when its centre of mass is directly below the point of suspension in the air

12 of 26

Where is the centre of mass for a rectangle?

Rectangles have two four lines of symmetry and these all cross at a single point in the centre of the rectangle. The point at which the axes all cross is where the centre of mass is

13 of 26

Explain how a tractor has been adapted to stay upright

The centre of mass for a tractor is in its engine which is deliberately low and close to the ground to give it a low centre of mass. This means that the tractor will have to tilt more to topple over 2)wide wheel base to decrease risk of toppling over

14 of 26

What is circular motion?

An object which constantly moves around in a circle goes through circular motion, where the object’s velocity is directed at a tangent to the circle

15 of 26

What is the motor effect?

The idea of a force being exerted on a wire with a current going through it which is passed through a magnetic field

16 of 26

How does an electric motor work?

It uses the motor effect. The current is reversed whenever the coil of wire spins half a turn, but because the sides swap over each half-turn also, the coil will continually spin in the same direction

17 of 26

What is electromagnetic induction?

The creation of potential difference across a conductor which is experiencing a change in magnetic field

18 of 26

What are transformers used for?

To change alternating potential differences

19 of 26

Explain when step-up and step-down transformers are used

A step-up transformer is used to bring the voltage of a power station up to the grid voltage, and a step-down transformer is used at the other end to step the grid voltage of the grid down to the voltage needed by our homes and offices